The objective of the proposed work is improved clinical applications of basic electrophysiologic information including improved clinical utility of electrocardiography. The objective will be approached with animal experiments and clinical observations. Body surface isopotential maps from 200 electrodes will be obtained from human subjects and dogs. In the latter, controlled activation sequence and thermal and other alterations of recovery properties will be employed to give known cardiac states. Body surface potential patterns associated with those will be determined and the relations established applied in the patient studies. The cardiac distribution of autonomic nerves and their effects on rhythm, electrophysiologic effects of ischemia and factors involved in initiation of arrhythmias will also be investigated.